Semiconductro laser device

ABSTRACT

This semiconductor laser device has the same structure as the conventional broad-area type semiconductor laser device, except that both side regions of light emission areas of active and clad layers are two-dimensional-photonic-crystallized. The two-dimensional photonic crystal formed on both side regions of the light emission area is the crystal having the property that 780 nm laser light cannot be wave-guided in a resonator direction parallel to a striped ridge within the region. The light traveling in the direction can exist only in the light emission area sandwiched between two photonic crystal regions, which results in the light laterally confined by the photonic crystal region. The optical confinement of the region suppresses the loss in the light at both edges of the stripe serving as the boundary of the optical confinement, which reduces the curve of wave surface and uniforms the light intensity distributions of NFP and FFP.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application of Divisionalapplication Ser. No. 11/790,532, filed Apr. 26, 2007, which is aDivisional Application of Parent application Ser. No. 10/702,604, filedNov. 2, 2003, now U.S. Pat. No. 7,248,612, issued Jul. 24, 2007. Thepresent application is based on Japanese Priority DocumentJP2002-338782, filed in the Japanese Patent Office on Nov. 22, 2002, theentire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor laser device and amethod of manufacturing the same, and relates more particularly to abroad-area type semiconductor laser device in which light intensitydistributions of a near field pattern (hereafter, referred to as NFP)and a far field pattern (hereafter, referred to as FFP) are uniform, andto a method of manufacturing such a semiconductor laser device.

2. Description of Related Art

The broad-area type semiconductor laser device in which a stripe widthis larger than 10 μm is frequently used for a light source of a laserprinter or a display apparatus, as a high output type semiconductorlaser device.

Here, the configuration of a conventional AlGaAs-based broad-area typesemiconductor laser device is described with reference to FIG. 5. FIG. 5is a sectional view showing the configuration of the AlGaAs-basedbroad-area type semiconductor laser device. A conventional AlGaAs-basedbroad-area type semiconductor laser device 10 (hereafter, referred to asa conventional semiconductor laser device 10) is the semiconductor laserdevice for oscillating a laser light whose wavelength is 780 nm. Asshown in FIG. 5, this has the multilayer structure composed of ann-Al_(0.7)Ga_(0.3)As clad layer 14, an n-Al_(0.3)Ga_(0.7)As guide layer16, an Al_(0.1)Ga_(0.9)As active layer 18, a p-Al_(0.3)Ga_(0.7)As guidelayer 20, a p-Al_(0.7)Ga_(0.3)As clad layer 22 and a p-GaAs cap layer24, which are grown sequentially on an n⁺-GaAs substrate 12.

In the multilayer structure, the upper layers of the p-GaAs cap layer 24and the p-AlGaAs clad layer 22 are processed as striped ridges, andn-GaAs current block layers 26 are embedded on both sides of the ridges.A p-side electrode 28 is formed on the p-GaAs cap layer 24 and then-GaAs current block layer 26, and an n-side electrode 30 is formed onthe rear surface of the n⁺-GaAs substrate 12.

When the above-mentioned conventional semiconductor laser device ismanufactured, the n-Al_(0.7)Ga_(0.3)As clad layer 14, then-Al_(0.3)Ga_(0.7)As guide layer 16, the Al_(0.1)Ga_(0.9)As active layer18, the p-Al_(0.3)Ga_(0.7)As guide layer 20, the p-Al_(0.7)Ga_(0.3)Asclad layer 22 and the p-GaAs cap layer 24 are epitaxially grownsequentially on the n⁺-GaAs substrate 12 by using a metal organicchemical vapor deposition method (MOCVD method) and the like.Consequently, the multilayer structure is formed. Next, in themultilayer structure, the upper layers of the p-GaAs cap layer 24 andthe p-AlGaAs clad layer 22 are etched to thereby form the stripedridges. Subsequently, the n-GaAs current block layers 26 are embeddedand grown on both sides of the ridges, and the ridges are embedded.Next, the p-side electrode 28 is formed on the p-GaAs cap layer 24 andthe n-GaAs current block layer 26, and the rear surface of the n⁺-GaAssubstrate 12 is polished to thereby adjust the thickness of thesubstrate. After that, the n-side electrode 30 is formed on the rearsurface (for example, refer to a non-patent document 1).

The lateral mode of the laser light emitted from the semiconductor laserdevice has a large influence on the suitability of the device propertyof the semiconductor laser device when the semiconductor laser device isapplied as the light source. In short, the lateral mode control tostably control the light mode in the lateral direction of the laserlight emitted from the semiconductor laser device to a basic (0-th) modeis one of the important points for the control of the semiconductorlaser device. In particular, the broad-area type semiconductor laserdevice as mentioned above has the wide stripe width. Thus, the lateralmode is apt to be a multi mode. Hence, it is difficult that the lightintensity distributions of the NFP and the FFP become uniform. If thesemiconductor laser device, in which the light intensity distributionsof the NFP and the FFP are not uniform, is used as the light sources forprinting and the like, the irregularity in the light intensity isbrought about to thereby bring about the irregularity in printedcharacters. Also, if this is applied to a display, the image quality ofa displayed image is deteriorated.

[Non-Patent Document 1]

“Basics and Application of Understandable Semiconductor Laser Device”Written by Shoji Hirata, Edited by Ohmsha Ltd. in 2001, pages 180 to182.

SUMMARY OF THE INVENTION

Accordingly, there has been a need to provide a semiconductor laserdevice in which the light intensity distributions of NFP and FFP areuniform, and a method of manufacturing the same.

By the way, the irregularities in the intensities of the NFP and the FFPare thought to be caused by the fact that a wave-guide surface iscurved, in addition to the fact that the lateral mode is a multi-modevibration. That is, the fact that the curve of the wave-guide surfacecauses the light intensity to tend to be concentrated on edges of bothsides of the stripe is thought to be one factor of the occurrence of theirregularities in the intensities of the NFP and the FFP. One of thecauses of the curved wave-guide surface results from the delay in thetravel of the wave-guidance because the loss of the light occurs at theedges of both sides of the stripe.

So, the present inventors thought up the idea of suppressing the loss ofthe light at both side edges of the stripe and suppressing the curve ofthe wave-guide surface and thereby uniforming the light intensitydistributions of the NFP and the FFP on the wave-guide surface in thesemiconductor laser device. Moreover, in the course of continuing withthe research to solve the above-mentioned problems, the presentinventors thought up the idea ofmulti-dimensional-photonic-crystallizing, for example,two-dimensional-photonic-crystallizing the regions on both sides of thelight emission area or on the light emission area. This is because thetwo-dimensional photonic crystallization enables the formation of thestructure in which the light having a particular wavelength traveling ina particular direction cannot exist, and enables the control of thewave-guide situation to the particular direction of the light having theparticular wavelength. The multi-dimensional-photonic-crystal, forexample, the two-dimensional photonic crystal, depending on thestructure design, disables the existence of the light having theparticular wavelength traveling in the particular direction, or enablesthe promotion of the wave-guidance in the particular direction of thelight having the particular wavelength, whereby the wave-guide situationcan be controlled.

Then, the present inventors discovered the fact that by introducing thetwo- or multi-dimensional photonic crystal region into any of the activelayer, the guide layer and the clad layer in the semiconductor laserdevice, and then defining the light emission area on the basis of thephotonic crystal region, and thereby controlling the traveling manner ofthe light wave-guided through the light emission area on the basis ofthe photonic crystal region, it is possible to uniform the lightintensity distributions of the NFP and the FFP in the semiconductorlaser device, and thereby possible to control the lateral mode.

The photonic crystal implies “artificial multi-dimensional periodicstructure having periodic property of level similar to wavelength oflight”, for example, as introduced on a page 1524 of “0 plus E” magazinein December 1999. It should be noted that “this does not indicateso-called optical crystal material”. The above-mentioned periodicityimplies the periodicity with regard to the distribution of refractiveindexes, in many cases. An example of the photonic crystal is alsoreported in the same magazine. The photonic crystals in which theperiodicities of the refractive index distributions are atwo-dimensional direction and a third-dimensional direction are referredto as a two-dimensional photonic crystal and a third-dimensionalphotonic crystal, respectively.

In other words, the photonic crystal is the structure in which unitshave different refractive indexes, each of the units has a size similarto a wavelength of a light, and the units are arrayed such thatrefractive indexes are periodically changed in one-dimension ormulti-dimensional area. This is expected as the material that enables anoptical device having an excellent optical property, which cannot beobtained from conventional optical materials, to be attained bydesigning the material and the structure depending on a purpose. Forexample, an optical wave-guide device, a polarization splitter, a doublerefraction device for a visible region, and the like, in which thephotonic crystal is used, are proposed.

In order to attain the above-mentioned purposes, from theabove-mentioned viewpoints, the semiconductor laser device according tothe present invention (hereafter, referred to as a first invention) is asemiconductor laser device having a multilayer structure including atleast an active layer, a guide layer and a clad layer, wherein regionson both sides of a light emission area in one of the active layer, theguide layer and the clad layer aremulti-dimensional-photonic-crystallized.

Preferably, the multi-dimensional-photonic-crystallized regions on bothsides of the light emission area are in the active layer and in theguide layer formed on the active layer, and further, themulti-dimensional-photonic-crystallized regions on both sides of thelight emission area are multi-dimensional-photonic-crystallized to astructure in which a laser light is not wave-guided in a resonatorlength direction. The multi-dimensional photonic crystallization iscarried out thereby to generate the particular region where the lightwave-guided in a resonator length direction cannot exist. Then, theparticular region is used to carry out an optical confinement. Thus, theloss of the light is suppressed at both edges of the stripe serving as aboundary of the confinement, namely, the boundary between the lightemission area and the particular region. The curve of a wave-guidesurface is reduced, and the light intensity distributions of the NFP andthe FFP are made uniform.

Another semiconductor laser device according to the present invention(hereafter, referred to as a second invention) is a semiconductor laserdevice having a multilayer structure including at least an active layer,a guide layer and a clad layer, wherein a region on a light emissionarea of the guide layer formed on the active layer or a region below alight emission area of the guide layer formed under the active layer ismulti-dimensional-photonic-crystallized. Moreover, regions below bothlight emission areas of the guide layer formed under the active layerand a compound semiconductor layer formed under the guide layer aremulti-dimensional-photonic-crystallized.

In the second invention, preferably, themulti-dimensional-photonic-crystallized region is formed in such a waythat the wave-guidance in the resonator length direction of the laserlight is promoted. The multi-dimensional-photonic-crystallized regionhas the crystal structure having the property to promote thewave-guidance of the laser light in the resonator length direction.Thus, the laser light traveling in the resonator direction is affectedby the photonic crystallization region and stably wave-guided in theresonator length direction.

In the multi-dimensional-photonic-crystallized region of the concreteembodiments in the first and second inventions, micro pores extended ina direction vertical to a P—N junction plane of the compoundsemiconductor layer constituting the multilayer structure are arrangedat a periodic array. The present invention can be applied without anyrestriction on the composition of the compound semiconductor layer ofthe multilayer structure constituting the semiconductor laser device andthe kind of the substrate. For example, it can be applied to thesemiconductor laser device of an AlGaAs-based, a GaN-based, an InP-basedand the like. In particular, it can be preferably applied to thebroad-area type semiconductor laser device in which the width of thelight emission area extended in the stripe shaped on the surfaceparallel to the P-N junction plane of the compound semiconductor layerconstituting the multilayer structure is 10 μm or more. Also, it can bepreferably applied to a so-called edge-emitting semiconductor laserdevice in which a light output direction is not vertical to the P-Njunction plane.

A method of manufacturing a semiconductor laser device according to thepresent invention (hereafter, referred to as a first invention method)is a method of manufacturing a semiconductor laser device having amultilayer structure including at least an active layer, a guide layerand a clad layer; including the steps of: growing a predeterminedcompound semiconductor layer, and forming the multilayer structurehaving the guide layer on the active layer; forming micro pores extendedin a multilayer direction of the multilayer structure so as to form aperiodic array, on both side regions of a light emission area of theguide layer, and carrying out amulti-dimensional-photonic-crystallization; growing the clad layer onthe guide layer that includes themulti-dimensional-photonic-crystallized region, and further forming apredetermined compound semiconductor layer thereon, to form themultilayer structure.

Another method of manufacturing a semiconductor laser device accordingto the present invention (hereafter, referred to as a second inventionmethod) is a method of manufacturing a semiconductor laser device havinga multilayer structure including at least an active layer, a guide layerand a clad layer; including the steps of: growing a predeterminedcompound semiconductor layer, and forming the multilayer structurehaving the guide layer on the active layer; forming micro pores extendedin a multilayer direction of the multilayer structure so as to form aperiodic array, on a region of a light emission area of the guide layer,and carrying out a multi-dimensional-photonic-crystallization; andgrowing the clad layer on the guide layer that includes themulti-dimensional-photonic-crystallized region, and further forming apredetermined compound semiconductor layer, to form the multilayerstructure.

At the step of forming the micro pores extended in the multilayerdirection of the multilayer structure so as to form the periodic arrayand then carrying out the multi-dimensional-photonic-crystallization,the typical photo lithography technique and etching processing techniqueare used to form the micro pores at the periodic array.

As mentioned above, according to the first invention, the regions onboth sides of the light emission area in any layer of the active layer,the guide layer and the clad layer aremulti-dimensional-photonic-crystallized, for example,two-dimensional-photonic-crystallized to thereby generate the particularregion, in which the light wave-guided in the resonator length directioncan not exist, on both sides of the light emission area. Then, theparticular region is used to carry out the optical confinement.Consequently, the loss of the light at both edges of the stripe servingas the boundary of the optical confinement, namely, the boundary betweenthe light emission area and the particular region is suppressed, whichreduces the curve of the wave-guide surface and uniforms the lightintensity distributions of the NFP and the FFP.

According to the second invention, the region on the light emission areaor below the light emission area of the guide layer, and the guide layerformed below the light emission area and the compound semiconductorlayer formed under the guide layer aremulti-dimensional-photonic-crystallized, for example,two-dimensional-photonic-crystallized, which thereby enables themulti-dimensional-photonic-crystallized region to have the crystalstructure having the property to promote the wave-guidance of the laserlight in the resonator length direction. Moreover, the laser lighttraveling in the resonator length direction is affected by the photoniccrystallization region and stably wave-guided in the resonator lengthdirection. Hence, the semiconductor laser device can be attained inwhich the light intensity distributions of the NFP and the FFP areuniform.

The first and second invention methods are suitable for the broad-areatype semiconductor laser device in which the stripe width of the lightemission area is 10 μm or more.

Each of the first and second invention methods attains the manufacturingmethod suitable for the semiconductor laser device according to thefirst and second inventions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a configuration of a semiconductorlaser device of a first embodiment;

FIGS. 2A, 2B are sectional views at main steps when the above-mentionedsemiconductor laser device 40 is manufactured in accordance with amethod in the first embodiment;

FIG. 3 is a sectional view showing a configuration of a semiconductorlaser device of a third embodiment;

FIGS. 4A, 4B are sectional views of the above-mentioned semiconductorlaser device 40 at main process steps when it is manufactured inaccordance with a method in a second embodiment; and

FIG. 5 is a sectional view showing a configuration of a conventionalbroad-area type semiconductor laser device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below in concreteand in detail by exemplifying embodiments and referring to the attacheddrawings. By the way, a film forming method, a composition and a filmthickness of a compound semiconductor layer, a ridge width, a processingcondition and the like, which are described in the followingembodiments, are one exemplification to easily understand the presentinvention. Thus, the present invention is not limited to thisexemplification.

First Embodiment of Semiconductor Laser Device

This embodiment is one example of the semiconductor laser deviceaccording to the present invention. FIG. 1 is a sectional view showingthe configuration of the semiconductor laser device of this embodiment.In the members shown in FIG. 1, the same symbols are given to the samemembers as those in FIG. 5. A semiconductor laser device 40 in thisembodiment is the broad-area type semiconductor laser device whoseoscillation wavelength is 780 nm. As shown in FIG. 1, this has the sameconfiguration and the same layer structure as the conventionalbroad-area type semiconductor laser device 10, except that thetwo-dimensional photonic crystallization is performed on regions 44 onboth sides of a light emission area 42 of an AlGaAs active layer 18 anda p-AlGaAs guide layer 20. Here, the light emission area 42 is theregion immediately under a striped p-GaAs cap layer 24 surrounded by ann-GaAs current block layer 26.

The structure of the two-dimensional photonic crystal formed in theregions 44 on both sides of the light emission area 42 is the structurein which innumerable micro pores extended in the direction vertical tothe substrate surface of an n⁺-GaAs substrate 12 are arranged in theregions 44 on both sides of the light emission area 42 in a periodicarray, as shown in FIG. 2B, and this is the crystal structure having theproperty that the laser light of 780 nm can not be wave-guided in adirection (a direction of a resonator length, namely, a directionrepresented by a narrow in FIG. 2B) parallel to a striped ridge withinthe region 44. Thus, the light of 780 nm traveling in the resonatordirection can exist only in the light emission area 42 surrounded by thetwo photonic crystal regions 44. Hence, it becomes at the situation of alateral optical confinement caused by the photonic crystal region 44.

In the semiconductor laser device 40 in this embodiment, as mentionedabove, the two-dimensional photonic crystallization is carried out tothereby generate the region 44 where the light wave-guided in theresonator length direction cannot exist, and the region 44 is used tocarry out the optical confinement. Thus, the loss of the light issuppressed at both edges of the stripe serving as the boundary of theoptical confinement, namely, the boundary between the region 42 and theregion 44. The curve of a wave-guide surface is reduced. Hence, thelight intensity distributions of the NFP and the FFP become uniform.

First Embodiment of Method of Manufacturing Semiconductor Laser Device

This embodiment is one example in which the manufacturing method of thesemiconductor laser device according to the first invention method isapplied to the above-mentioned manufacturing of the semiconductor laserdevice 40. FIGS. 2A, 2B are sectional views of the above-mentionedsemiconductor laser device 40 at the main process steps when it ismanufactured in accordance with the method in this embodiment. In themembers shown in FIGS. 2A, 2B, the same symbols are given to the samemembers as those in FIG. 5. In accordance with the method of thisembodiment, when the above-mentioned semiconductor laser device 40 ismanufactured, at first, the n-Al_(0.7)Ga_(0.3)As clad layer 14, then-Al_(0.3)Ga_(0.7)As guide layer 16, the Al_(0.1)Ga_(0.9)As active layer18 and the p-Al_(0.3)Ga_(0.7)As guide layer 20 are epitaxially grownsequentially on the n⁺-GaAs substrate 12 by using the metal organicchemical vapor deposition method (MOCVD method) and the like, as shownin FIG. 2A, similarly to the conventional method, whereby the multilayerstructure is formed.

After the formation of the multilayer structure, a wafer is taken out ofa crystal growing apparatus. Subsequently, a mask (not shown) that hasthe pattern in which micro pores are arrayed at a periodic array on theregion 44 where the photonic crystallization is performed, namely, thestripe-shaped region 44 on both sides of the light emission area 42 andperfectly covers the regions except the regions 44 including the lightemission area 42 is formed on the p-AlGaAs guide layer 20. For example,photo-resist, SiO₂ and the like are used for the mask material. Next, aproper etching method, such as an RIE (Reactive Ion Etching) method andthe like, is used to etch the AlGaAs active layer 18 and the p-AlGaAsguide layer 20. When the mask is removed after the etching, the micropores 46 are formed at the same periodic array as the periodic array ofthe micro pores formed on the mask, on the region 44 in the p-AlGaAsguide layer 20 and in the AlGaAs active layer 18, as shown in FIG. 2B.Consequently, the two-dimensional photonic crystallization is attained.The depth in the photonic crystallization can be adjusted by adjustingthe etching condition and thereby controlling the depth of the vacancies26.

Next, the wafer is again set in the crystal growing apparatus. Then, thep-Al_(0.7)Ga_(0.3)As clad layer 22 and the p-GaAs cap layer 24 areepitaxially grown to thereby form the multilayer structure.Subsequently, similarly to the conventional method, the ridge is formedand embedded, and the p-side electrode 28 and the n-side electrode 30are formed.

Second Embodiment of Semiconductor Laser Device

This embodiment is another example of the semiconductor laser deviceaccording to the first invention. In the first embodiment, the region 44is photonic-crystallized and has the structure of the two-dimensionalphotonic crystal. However, in this embodiment, the region 44 isthree-dimensional-photonic-crystallized by a micro processing technique.In the three-dimensional photonic crystal, the proper design of thephotonic crystal structure enables the attainment of the condition atwhich the light having a particular wavelength is never propagatedindependently of a direction, namely, the light having the particularwavelength can not exist at all. So, the introduction of thethree-dimensional photonic crystal structure into the regions 44 enablesthe regions 44 on both sides of the light emission area 42 to be theregion where the laser light cannot exist at all. Thus, in thisembodiment, the loss of the light at both edges of the stripe is furthersuppressed over the first embodiment introducing the two-dimensionalphotonic crystal, and the curve of a wave-guide surface is reducedthereby to make uniform the light intensity distributions of the NFP andthe FFP.

Third Embodiment of the Semiconductor Laser Device

This embodiment is one example of the semiconductor laser deviceaccording to the second invention. FIG. 3 is a sectional view showingthe configuration of the semiconductor laser device of this embodiment.In the members shown in FIG. 3, the same symbols are given to the samemembers as those in FIG. 5. A semiconductor laser device 50 in thisembodiment is a broad-area type semiconductor laser device whoseoscillation wavelength is 780 nm. As shown in FIG. 3, this has the sameconfiguration and the same layer structure as the conventionalbroad-area type semiconductor laser device 10, except that the a region54 of the p-AlGaAs guide layer 20 on a light emission area 52 istwo-dimensional-photonic-crystallized.

The structure of the two-dimensional photonic crystal formed on theregion 54 of the p-AlGaAs guide layer 20 is the structure in which theinnumerable micro pores extended in the direction vertical to thesubstrate surface of the n⁺-GaAs substrate 12 are arranged in theregions 54 on the light emission area 52 in a periodic array, as shownin FIG. 4B, and this is the crystal structure having the property thatthe laser light of 780 nm promotes the wave guidance in a direction (adirection of a resonator length, namely, a direction represented by anarrow in FIG. 4B) parallel to the striped ridge. In other words, thestructure of the two-dimensional photonic crystal shown in FIG. 2B isthe structure to promote the light, in which the oscillation wavelengthof the laser is, for example, 780 nm, to be wave-guided in the arrowdirection (the direction of the resonator) in FIG. 4B. Thus, it isdifficult that the light in the direction different from the arrowdirection is wave-guided.

Consequently, the light of 780 nm traveling in the resonator directionis affected by the photonic crystallized region 44 and stablywave-guided in the resonator length direction (the arrow direction inFIG. 4B). Also, the vacancies constituting the photonic crystalstructure are uniformly formed throughout the region 54 at the equalinterval. Thus, the influence of the wave-guidance also promoted by theregion 54 has the uniform influence on the entire area within the stripe(the light emission area). Hence, the light is wave-guided at theuniform intensity within the stripe. In this way, the region where thewave-guidance in the particular direction of the light having theparticular wavelength is promoted is used to carry out the opticalconfinement, which can attain the stabilization and the uniformity ofthe intensities of the wave-guided lights and can also uniform the lightintensity distributions of the NFP and the FFP.

Second Embodiment of Method of Manufacturing Semiconductor Laser Device

This embodiment is one example in which the manufacturing method of thesemiconductor laser device according to the second invention method isapplied to the above-mentioned manufacturing of the semiconductor laserdevice 50. FIGS. 4A, 4B are respective sectional views of theabove-mentioned semiconductor laser device 50 at the main process stepswhen it is manufactured in accordance with the method in thisembodiment. In the members shown in FIGS. 4A, 4B, the same symbols aregiven to the same members as those in FIG. 5. In accordance with themethod of this embodiment, when the above-mentioned semiconductor laserdevice 50 is manufactured, at first, the n-Al_(0.7)Ga_(0.3)As clad layer14, the n-Al_(0.3)Ga_(0.7)As guide layer 16, the Al_(0.1)Ga_(0.9)Asactive layer 18 and the p-Al_(0.3)Ga_(0.7)As guide layer 20 areepitaxially grown sequentially on the n⁺-GaAs substrate 12 by using themetal organic chemical vapor deposition method (MOCVD method) and thelike, similarly to the conventional method, whereby the multilayerstructure is formed.

After the formation of the multilayer structure, the wafer is taken outof the crystal growing apparatus. Subsequently, on the region 54 wherethe photonic crystallization is performed, namely, the region 54 on thelight emission area 52 of the p-AlGaAs guide layer 20, a mask (notshown) that has the pattern in which the micro pores are arrayed at theperiodic array and perfectly covers the regions except the region 54 isformed on the p-AlGaAs guide layer 20. For example, the photo-resist,the SiO₂ and the like are used for the mask material. Next, the properetching method, such as the RIE (Reactive Ion Etching) method and thelike, is used to etch the p-AlGaAs guide layer 20. When the mask isremoved after the etching, the micro pores 56 are formed at the sameperiodic array as the periodic array of the micro pores formed on themask, on the region 54 of the p-AlGaAs guide layer 20, as shown in FIG.4B. Consequently, the two-dimensional photonic crystallization isattained. The depth in the photonic crystallization can be adjusted byadjusting the etching condition and thereby controlling the depth of thevacancies 56.

Next, the wafer is again set in the crystal growing apparatus. Then, thep-Al_(0.7)Ga_(0.3)As clad layer 22 and the p-GaAs cap layer 24 areepitaxially grown to thereby form the multilayer structure.Subsequently, similarly to the conventional method, a ridge is formedand embedded, and the p-side electrode 28 and the n-side electrode 30are formed.

In this embodiment, the region 54 on the light emission area 52 isphotonic-crystallized. A width of the region 54 on which the photoniccrystallization is performed does not need to be perfectly coincidentwith a width of the light emission area 52. It may be the region 54having a width slightly larger than that of the light emission area 52.Also, in this embodiment, it is necessary to define a thickness in sucha way that a thickness of the layer on which the photoniccrystallization is performed is a thickness in a range in which theactive layer 18 is not damaged and that the light wave-guided throughthe active layer 18 receives the influence of the photoniccrystallization region.

Fourth Embodiment of Semiconductor Laser Device

This embodiment is still another example of the semiconductor laserdevice according to the second invention. In the third embodiment, theregion 54 of the p-AlGaAs guide layer 20 is photonic-crystallized sothat it has the structure of the two-dimensional photonic crystal.However, in this embodiment, although not shown, the region below thelight emission area 52 of the n-AlGaAs guide layer 16 and the region ofthe n-AlGaAs clad layer 14 under it aretwo-dimensional-photonic-crystallized. Thus, it is possible to providethe same effect as the third embodiment. When the semiconductor laserdevice in this embodiment is manufactured, after the formation of then-AlGaAs guide layer 16, the predetermined region isphotonic-crystallized similarly to the manufacturing method of thesemiconductor laser device in the second embodiment. Subsequently,similarly to the conventional method, the layers on and after the AlGaAsactive layer 18 is epitaxially grown to thereby form the multilayerstructure. Then, the ridge is formed, and the semiconductor laser deviceis manufactured.

In the first to fourth embodiments of the semiconductor laser device andthe first and second embodiments of the manufacturing method of thesemiconductor laser device, they have been explained by exemplifying theAlGaAs-based semiconductor laser device. However, the present inventionis not limited to the AlGaAs-based semiconductor laser device.Naturally, it can be applied to even a semiconductor laser device of aGaN-based, an InP-based and the like.

Finally, the embodiments and examples described above are only examplesof the present invention. It should be noted that the present inventionis not restricted only to such embodiments and examples, and variousmodifications, combinations and sub-combinations in accordance with itsdesign or the like may be made without departing from the scope of thepresent invention.

1. A method of manufacturing a semiconductor laser device, the methodcomprising the steps of: forming an active layer between a first guidelayer of a first conductivity type and a second guide layer of a secondconductivity type; forming micro pores within said first guide layer,and thereafter; forming a first clad layer of the first conductivitytype between a cap layer of the first conductivity type and said firstguide layer, wherein a light emission area of said active layer has nosaid micro pores, wherein said micro pores are within said active layer,wherein said micro pores form a periodic array.
 2. The method accordingto claim 1, wherein said second conductivity type is opposite to saidfirst conductivity type.
 3. The method according to claim 1, whereinsaid first clad layer has no said micro pores.
 4. The method accordingto claim 1, wherein said second guide layer has no said micro pores. 5.The method according to claim 1, wherein a striped ridge of said firstclad layer separates current block layers.
 6. The method according toclaim 1, wherein said micro pores are between said second guide layerand said striped ridge.
 7. The method according to claim 1, wherein saidmicro pores are between said second guide layer and said current blocklayers.
 8. The method according to claim 1, wherein said micro pores areformed by an etching method.
 9. The method according to claim 1, whereinsaid second guide layer is an n-Al_(0.3)Ga_(0.7)As layer.
 10. The methodaccording to claim 1, wherein said active layer is an Al_(0.1)Ga_(0.9)Aslayer.
 11. The method according to claim 1, wherein said first guidelayer is a p-Al_(0.7)Ga_(0.7)As layer.
 12. The method according to claim1, wherein said first clad layer is a p-Al_(0.7)Ga_(0.3)As layer. 13.The method according to claim 1, wherein said cap layer is a p-GaAslayer.
 14. The method according to claim 1, wherein a second clad layerof the second conductivity type is between said second guide layer ofthe second conductivity type and a substrate.
 15. The method accordingto claim 14, wherein said second clad layer is an n-Al_(0.7)Ga_(0.3)Aslayer.
 16. The method according to claim 14, wherein said substrate isan n-GaAs substrate.
 17. The method according to claim 14, wherein saidmicro pores extended in a direction vertical to said substrate.